# Patent

## Title
Control system for fluorescent light fixture

## Abstract

A ballast module for a fluorescent light comprises an electrolytic capacitance element. A temperature sensor senses a temperature of the electrolytic capacitance element. A control module communicates the temperature sensor and adjusts power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 60/672,250, filed on Apr. 18, 2005. The disclosure of the above application is incorporated herein by reference.


FIELD OF THE INVENTION
The present invention relates to fluorescent light fixtures, and more particularly to control systems for fluorescent light fixtures.
BACKGROUND OF THE INVENTION
Referring now to FIG. 1, a fluorescent lamp 10 includes a sealed glass tube 12 that contains a first material such as mercury and a first inert gas such as argon, which are both generally identified at 14. The tube 12 is pressurized. Phosphor powder 16 may be coated along an inner surface of the tube 12. The tube 12 includes electrodes 18A and 18B (collectively electrodes 18) that are located at opposite ends of the tube 12. Power is supplied to the electrodes 18 by a control system that may include an AC source 22, a switch 24, a ballast module 26 and a capacitor 28.
When the switch 24 is closed, the control system supplies power to the electrodes 18. Electrons migrate through the gas 14 from one end of the tube 12 to the opposite end. Energy from the flowing electrons changes some of the mercury from a liquid to a gas. As electrons and charged atoms move through the tube 12, some will collide with the gaseous mercury atoms. The collisions excite the atoms and cause electrons to move to a higher state. As the electrons return to a lower energy level they release photons or light. Electrons in mercury atoms release light photons in the ultraviolet wavelength range. The phosphor coating 16 absorbs the ultraviolet photons, which causes electrons in the phosphor coating 16 to jump to a higher level. When the electrons return to a lower energy level, they release photons having a wavelength corresponding to white light.
To send current through the tube 12, the fluorescent light 10 needs free electrons and ions and a difference in charge between the electrodes 18. Generally, there are few ions and free electrons in the gas 14 because atoms typically maintain a neutral charge. When the fluorescent light 10 is turned on, it needs to introduce new free electrons and ions.
The ballast module 26 outputs current through both electrodes 18 during starting. The current flow creates a charge difference between the two electrodes 18. When the fluorescent light 10 is turned on, both electrode filaments heat up very quickly. Electrons are emitted, which ionizes the gas 14 in the tube 12. Once the gas is ionized, the voltage difference between the electrodes 18 establishes an electrical arc. The flowing charged particles excite the mercury atoms, which triggers the illumination process. As more electrons and ions flow through a particular area, they bump into more atoms, which frees up electrons and creates more charged particles. Resistance decreases and current increases. The ballast module 26 regulates power both during and after startup.
Referring now to FIG. 2, some ballast modules 50 include a control module 54, one or more electrolytic capacitors 56 and other components 58. The electrolytic capacitors 56 may be used to filter or smooth voltage. Electrolytic capacitors 56 and/or other system components may be sensitive to high operating temperatures. If the operating temperature exceeds a threshold for a sufficient period, the electrolytic capacitor 56 and/or other system components may be damaged and the fluorescent light 10 may become inoperable.
SUMMARY OF THE INVENTION
A ballast module for a fluorescent light comprises an electrolytic capacitance element. A temperature sensor senses a temperature of the electrolytic capacitance element. A control module communicates the temperature sensor and adjusts power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the control module reduces the power output to the fluorescent light. The control module reduces the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module turns off the power output to the fluorescent light. The control module turns off the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module modulates the power output based on the sensed temperature.
A system comprises the ballast module and further comprises a switch that selectively provides power to the control module. The switch is a three-way switch. A rectifier module has an input that selectively communicates with a voltage source. The electrolytic capacitance element and the control module communicate with an output of the rectifier module.
In other features, the ballast module further comprises a first power transistor having a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control module. A second power transistor has a first terminal that communicates with a second terminal of the first power transistor, and a control terminal that communicates with the control module. A second capacitance element communicates with the first and second terminals of the first power transistor. An inductance element has one end that communicates with the second terminal of the first power transistor and an opposite end that communicates with an electrode of the fluorescent light.
A system comprises the ballast module and further comprises the fluorescent light having first and second pairs of electrodes. A third capacitance element communicates with one of the first pair of electrodes and one of the second pair of electrodes. A system comprises the ballast module and further comprises the fluorescent light having first and second pairs of electrodes. A fourth capacitance element communicates with one of the first pair of electrodes and the second capacitance element.
A ballast module for a fluorescent light comprises electrolytic capacitance means for providing capacitance. Temperature sensing means senses a temperature of the electrolytic capacitance means. Control means communicates with the temperature sensing means for adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the control means reduces the power output to the fluorescent light. The control means reduces the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means turns off the power output to the fluorescent light. The control means turns off the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means modulates the power output based on the sensed temperature.
A system comprises the ballast module and further comprises switching means for selectively providing power to the control means. The switching means is a three-way switching means. Rectifier means for rectifying has an input that selectively communicates with a voltage source. The electrolytic capacitance means and the control means communicate with an output of the rectifier means. First power switching means for switching has a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control means. Second power switching means for switching has a first terminal that communicates with a second terminal of the first power switching means, and a control terminal that communicates with the control means. Second capacitance means for providing capacitance communicates with the first and second terminals of the first power switching means. Inductance means for providing inductance has one end that communicates with the second terminal of the first power switching means and an opposite end that communicates with an electrode of the fluorescent light.
A system comprises the ballast module and further comprises the fluorescent light having first and second pairs of electrodes. Third capacitance means for providing capacitance communicates with one of the first pair of electrodes and one of the second pair of electrodes. A system comprises the ballast module and further comprises the fluorescent light having first and second pairs of electrodes. Fourth capacitance means for providing capacitance and that communicates with one of the first pair of electrodes and the second capacitance means.
A method for operating a ballast module for a fluorescent light comprises providing an electrolytic capacitance element in the ballast module; sensing a temperature of the electrolytic capacitance element; and adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the method includes reducing the power output to the fluorescent light. The method includes reducing the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes turning off the power output to the fluorescent light. The method includes turning off the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes modulating the power output based on the sensed temperature. The method includes selectively providing power to the control module.
A control system for a fluorescent light comprises a first electrical component. A temperature sensor senses a temperature of the first electrical component. A control module communicates with the temperature sensor and adjusts power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the control module reduces the power output to the fluorescent light. The control module reduces the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module turns off the power output to the fluorescent light. The control module turns off the power output for a predetermined period. The control module increases power output to the fluorescent light after the predetermined period. The control module modulates the power output based on the sensed temperature.
The control system further comprises a switch that selectively provides power to the control module. The switch is a three-way switch. A rectifier module has an input that selectively communicates with a voltage source. The electrolytic capacitance element and the control module communicate with an output of the rectifier module.
In other features, the control system further comprises a first power transistor having a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control module. A second power transistor has a first terminal that communicates with a second terminal of the first power transistor, and a control terminal that communicates with the control module. A second capacitance element communicates with the first and second terminals of the first power transistor. An inductance element has one end that communicates with the second terminal of the first power transistor and an opposite end that communicates with an electrode of the fluorescent light.
The control system further comprises the fluorescent light having first and second pairs of electrodes. A third capacitance element communicates with one of the first pair of electrodes and one of the second pair of electrodes. The control system further comprises the fluorescent light having first and second pairs of electrodes. A fourth capacitance element communicates with one of the first pair of electrodes and the second capacitance element.
A control system for a fluorescent light comprises first means for providing a first electrical function. Temperature sensing means senses a temperature of the first means. Control means communicates with the temperature sensing means for adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the control means reduces the power output to the fluorescent light. The control means reduces the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means turns off the power output to the fluorescent light. The control means turns off the power output for a predetermined period. The control means increases power output to the fluorescent light after the predetermined period. The control means modulates the power output based on the sensed temperature.
The control system further comprises switching means for selectively providing power to the control means. The switching means is a three-way switching means. Rectifier means for rectifying has an input that selectively communicates with a voltage source. The electrolytic capacitance means and the control means communicate with an output of the rectifier means. First power switching means for switching has a first terminal that communicates with a first output terminal of the rectifier and a control terminal that communicates with the control means. Second power switching means for switching has a first terminal that communicates with a second terminal of the first power switching means, and a control terminal that communicates with the control means. Second capacitance means for providing capacitance communicates with the first and second terminals of the first power switching means. Inductance means for providing inductance has one end that communicates with the second terminal of the first power switching means and an opposite end that communicates with an electrode of the fluorescent light.
The control system further comprises the fluorescent light having first and second pairs of electrodes. Third capacitance means for providing capacitance communicates with one of the first pair of electrodes and one of the second pair of electrodes. The control system further comprises the fluorescent light having first and second pairs of electrodes. Fourth capacitance means for providing capacitance and that communicates with one of the first pair of electrodes and the second capacitance means.
A method for operating a control system for a fluorescent light comprises providing a first electrical component; sensing a temperature of the first electrical component; and adjusting power output to the fluorescent light when the sensed temperature exceeds a predetermined threshold.
In other features, the method includes reducing the power output to the fluorescent light. The method includes reducing the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes turning off the power output to the fluorescent light. The method includes turning off the power output for a predetermined period. The method includes increasing power output to the fluorescent light after the predetermined period. The method includes modulating the power output based on the sensed temperature. The method includes selectively providing power to the control module.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a functional block diagram of an exemplary control system for a fluorescent light according to the prior art;
FIG. 2 is a more detailed functional block diagram of the control system for the fluorescent light of FIG. 1;
FIG. 3 is a functional block diagram of an improved control system for a fluorescent light according to the present invention;
FIG. 4 is an electrical schematic and functional block diagram of an exemplary implementation of the control system of FIG. 3;
FIG. 5 is a first exemplary flowchart illustrating steps for operating the control system of FIG. 3;
FIG. 6 is a second exemplary flowchart illustrating steps for operating the control system of FIG. 3; and
FIG. 7 is a third exemplary flowchart illustrating steps for operating the control system of FIG. 3.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements.
Referring now to FIG. 3, a functional block diagram of a control system 98 for the fluorescent light 10 is shown. A ballast module 100 includes a control module 104, one or more electrolytic capacitors 108, and one or more other components generally identified at 110. The ballast module 100 includes one or more temperature sensing modules 112 and 114 that sense operating temperatures of components of the ballast module 100 and/or of the control system of the florescent light 10. In some implementations, the temperature sensor 112 senses an operating temperature of the electrolytic capacitor 108 and the temperature sensor 114 senses an operating temperature of one or more other components 110 of the ballast module 100 and/or the control system.
The control module 104 adjusts operation of the fluorescent light 10 based on one or more of the sensed operating temperatures. For example, the control module 104 shuts off the florescent light 10 when the operating temperature of the electrolytic capacitor 56 exceeds a predetermined temperature threshold. Alternately, the control module 104 turns off the florescent light 10 for a predetermined period, until reset, indefinitely and/or using other criteria. In other implementations, the control module 104 lowers an output voltage and/or current of the ballast module 100 for a predetermined period, indefinitely, until reset and/or using other criteria.
Referring now to FIG. 4, an exemplary implementation of the ballast module 100 is shown to include a full or half-wave rectifier 120, the electrolytic capacitor 106 and the control module 104. A first terminal of a power transistor 126 is connected to a first output of the rectifier 120. A second terminal is connected to the control module 104 and to a first terminal of a power transistor 128. The control module 104 switches the power transistors on and off to vary current and/or voltage to the florescent light 10 during startup and/or operation.
A capacitor C1 may be connected to the first output of the rectifier 120, the second terminal of the power transistor 126, the first terminal of the power transistor 128 and one end of an inductor L. An opposite end of the inductor L may communicate with one end of the electrode 18A. An opposite end of the electrode 18A is coupled by a capacitor C3 to one end of the electrode 18B. The first output of the rectifier 120 is coupled by a capacitor C2 to an opposite end of the electrode 18B.
Referring now to FIG. 5, a flowchart illustrating steps for operating the control system of FIG. 3 is shown. Control begins with step 200. In step 204, control determines whether the switch 24 is on. If false, control returns to step 204. If step 204 is true, control determines whether the florescent light 10 is already on. If true, control continues with step 208 and determines whether a sensed temperature is greater than a threshold temperature. The sensed temperature may relate to the electrolytic capacitor 56 and/or other components of the ballast module 100 and/or other components of the control system. If step 206 is false, control starts the light in step 214 continues with step 208. If step 208 is false and the threshold temperature has not been exceeded, control determines whether the switch 24 is off in step 210. If the switch 24 is not off, control returns to step 204.
When step 208 is true, control turns off the switch 24 and/or florescent light 10 in step 216. In some implementations, the switch 24 may be controlled by the control module 104. Alternately, the control module 104 may turn off the florescent light 10 independent from a position of the switch 24. Alternately, the control module 104 may operate as a three way switch in conjunction with a three-way switch 24. When step 210 is true and the switch 24 is off, control turns off the florescent light 10 in step 218.
Referring now to FIG. 6, a flowchart illustrating alternate steps for operating the control system of FIG. 3 is shown. When step 208 is false, control returns to step 204. When step 208 is true, control turns off the florescent light 10 in step 242. In step 246, control starts a timer. In step 250, control determines whether the timer is up. If step 250 is true, control returns to step 204. Otherwise, control returns to step 250.
Referring now to FIG. 7, a flowchart illustrating alternative steps for operating the control system of FIG. 3 is shown. When step 208 is true, control reduces power that is output to the florescent light 10 in step 282. Reducing power output to the florescent light 10 may include reducing voltage and/or current output by the ballast module 100. The florescent light 10 may be operated in this mode until reset using the switch 24. Alternately in step 286, control starts a timer. In step 290, control determines whether the timer is up. If step 290 is true, control returns to step 204. Otherwise, control returns to step 290.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. For example, the temperature of a component can be sensed and the power output can be modulated accordingly. Hysteresis, averaging and/or other techniques can be used to reduce flicker and/or other noticeable changes in light intensity that may occur. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.

## Claims

1. A ballast module for a fluorescent light, the ballast module comprising:
an electrolytic capacitance element;
a temperature sensor that senses a temperature of said electrolytic capacitance element; and
a control module that communicates said temperature sensor and that adjusts power output to the fluorescent light when said sensed temperature exceeds a predetermined threshold,
wherein said control module reduces said power output for a predetermined period and increases said power output after said predetermined period.

2. The ballast module of claim 1 wherein said control module turns off said power output to the fluorescent light when reducing said power output.

3. The ballast module of claim 1 wherein said control module turns off said power output for said predetermined period when reducing said power output.

4. The ballast module of claim 1 wherein said control module modulates said power output based on said sensed temperature.

5. A system comprising the ballast module of claim 1 and further comprising a switch that selectively provides power to said control module.

6. The system of claim 5 wherein said switch is a three-way switch.

7. The ballast module of claim 1 further comprising a rectifier module having an input that selectively communicates with a voltage source, wherein said electrolytic capacitance element and said control module communicate with an output of said rectifier module.

8. The ballast module of claim 7 further comprising:
a first power transistor having a first terminal that communicates with a first output terminal of said rectifier, and a control terminal that communicates with said control module; and
a second power transistor having a first terminal that communicates with a second terminal of said first power transistor, and a control terminal that communicates with said control module.

9. The ballast module of claim 8 further comprising a second capacitance element that communicates with said first and second terminals of said first power transistor.

10. The ballast module of claim 9 further comprising an inductance element having one end that communicates with said second terminal of said first power transistor and an opposite end that communicates with an electrode of the fluorescent light.

11. A system comprising the ballast module of claim 9 and further comprising:
the fluorescent light having first and second pairs of electrodes; and
a fourth capacitance element that communicates with one of said first pair of electrodes and said second capacitance element.

12. A system comprising the ballast module of claim 1 and further comprising:
the fluorescent light having first and second pairs of electrodes; and
a third capacitance element that communicates with one of said first pair of electrodes and one of said second pair of electrodes.

13. A ballast module for a fluorescent light, the ballast module comprising:
electrolytic capacitance means for providing capacitance;
temperature sensing means for sensing a temperature of said electrolytic capacitance means; and
control means that communicates with said temperature sensing means, said control means for adjusting power output to the fluorescent light when said sensed temperature exceeds a predetermined threshold,
wherein said control means reduces said power output for a predetermined period and increases said power output after said predetermined period.

14. The ballast module of claim 13 wherein said control means turns off said power output to the fluorescent light when reducing said power output.

15. The ballast module of claim 13 wherein said control means turns off said power output for said predetermined period when reducing said power output.

16. The ballast module of claim 13 wherein said control means modulates said power output based on said sensed temperature.

17. A system comprising the ballast module of claim 13 and further comprising switching means for selectively providing power to said control means.

18. The system of claim 17 wherein said switching means is a three-way switching means.

19. The ballast module of claim 13 further comprising rectifier means for rectifying and having an input that selectively communicates with a voltage source, wherein said electrolytic capacitance means and said control means communicate with an output of said rectifier means.

20. The ballast module of claim 19 further comprising:
first power switching means for switching and having a first terminal that communicates with a first output terminal of said rectifier, and a control terminal that communicates with said control means; and
second power switching means for switching and having a first terminal that communicates with a second terminal of said first power switching means, and a control terminal that communicates with said control means.

21. The ballast module of claim 20 further comprising second capacitance means for providing capacitance and that communicates with said first and second terminals of said first power switching means.

22. The ballast module of claim 21 further comprising inductance means for providing inductance and having one end that communicates with said second terminal of said first power switching means and an opposite end that communicates with an electrode of the fluorescent light.

23. A system comprising the ballast module of claim 21 and further comprising:
the fluorescent light having first and second pairs of electrodes;
fourth capacitance means for providing capacitance and that communicates with one of said first pair of electrodes and said second capacitance means.

24. A system comprising the ballast module of claim 13 and further comprising:
the fluorescent light having first and second pairs of electrodes;
third capacitance means for providing capacitance and that communicates with one of said first pair of electrodes and one of said second pair of electrodes.

25. A method for operating a ballast module for a fluorescent light, comprising:
providing an electrolytic capacitance element in the ballast module;
sensing a temperature of said electrolytic capacitance element;
adjusting power output to the fluorescent light when said sensed temperature exceeds a predetermined threshold;
reducing said power output for a predetermined period; and
increasing said power output after said predetermined period.

26. The method of claim 25 further comprising turning off said power output to the fluorescent light when reducing said power output.

27. The method of claim 25 further comprising turning off said power output for said predetermined period when reducing said power output.

28. The method of claim 25 further comprising modulating said power output based on said sensed temperature.

29. The method of claim 25 further comprising selectively providing power to said control module.